1. Field of the Invention
The present invention relates to an apparatus of catalyst-circulation type for decomposing waste plastics and organics, and to a system thereof at high efficiency. The decomposition apparatus further includes a means for separating and recovering metals and inorganics which are mixed in the waste plastics or which are vapor-deposited or adhered to at least a portion of the waste plastics.
This application claims the priority of Japanese Patent Application No. 2006-115920, No. 2006-115925 and No. 2007-016087.
2. Related Background of the Invention
Organics such as plastics are difficult for treating on discarding them. Incineration treatment of them raises a danger of generating toxic substances such as dioxins.
Plastics pieces often contain metals such as aluminum and copper, and inorganics, and have metals vapor-deposited or adhered to the surface of plastics, depending on the uses of the plastics. If those plastics pieces are incinerated, toxic gases may be generated or the incineration furnace may be damaged.
Accordingly, organics such as plastics pieces are treated by landfilling in some cases. As plastics, however, they are not decomposed in the ground. In addition, the availability of landfill sites has become difficult. Although there are biodegradable plastics, they have drawbacks of taking a long period of time until they are decomposed and of need of a very large area for biodegradation. Furthermore, reusable metals, rare metals, and inorganics mixed in the waste plastics and organics cannot be separated therefrom, and they are simply landfilled or incinerated together with the waste plastics and organics.
There exists a conventional process for decomposing organics utilizing a catalyst, as illustrated in FIG. 11. According to the existing process, organics such as plastics are crushed into granules in a crusher 101, and then the crushed organics are charged into a reactor 102 in drum shape, the reactor 102 containing catalyst granules in advance. After that, agitation blades 103 are rotated in the reactor 102 to agitate the catalyst with the organics, while supplying hot air into the reactor 102 using an air-supply blower 104. The work of the catalyst enhances the decomposition of the organics, thus the organics are gasified.
Although the catalyst is left behind in the reactor 102, the gasified organics pass through a separator 106 consisting mainly of cyclone dust collector, and only water vapor and carbon dioxide are emitted to atmosphere as the exhaust gas. By above gasification of the organics charged into the reactor 102, new organics at an amount corresponding to the amount of gasified organics can be charged to the reactor 102, thereby allowing the above process to continuously operate without interruption.
Above existing decomposition apparatus, however, cannot conduct efficient treatment for decomposing waste plastics, and requires large treatment cost and large apparatus.
Furthermore, the treatment of waste containing polyvinylchloride is known to generate hydrogen chloride gas and nitrogen compounds. In addition, the treatment of Teflon® is known to generate toxic hydrogen fluoride gas. The treatment of those kinds of gases becomes a problem.
Regarding the prevention of secondary infection caused by infectious medical waste discharged from hospitals, dialysis facilities, and the like, a guideline specifying the treatment method of that kind of waste was issued from the Ministry of Health and Welfare on Nov. 17, 1999, and was enforced on Apr. 1, 2000. The guideline orders the hospitals, dialysis facilities, and the like to conduct in-house sterilization of the medical waste, in principle.
In this regard, there is wanted the development of a decomposition method for waste plastics, in particular the infectious medical waste containing polyvinylchloride, applicable in hospitals or clinics safely without using large scale apparatus.
Other than above-described method, the technologies relating to the decomposition of plastics and the like are disclosed in the following Patent Documents 1 to 5.
[Patent Document 1] Japanese Patent Application Laid-Open No. 2002-363337
[Patent Document 2] Japanese Patent Application Laid-Open No. 2004-182837
[Patent Document 3] Japanese Patent Application Laid-Open No. 2005-066433
[Patent Document 4] Japanese Patent Application Laid-Open No. 2005-205312
[Patent Document 5] Japanese Patent Application Laid-Open No. 2005-307007